It is important to view knowledge as sort of a semantic tree -- make sure you understand the fundamental principles, ie the trunk and big branches, before you get into the leaves/details or there is nothing for them to hang on to.
As to methods there may be a million and then some, but principles are few. The man who grasps principles can successfully select his own methods. The man who tries methods, ignoring principles, is sure to have trouble.
The only objects of practical reason are therefore those of good and evil. For by the former is meant an object necessarily desired according to a principle of reason; by the latter one necessarily shunned, also according to a principle of reason.